Powder, Fire, Glass: The Reproduction of Blue Enamels and the Role of Fire in Seventeenth- and Eighteenth-Century Instructions

In the study of early modern glassmaking, scholarship has traditionally focused on the production of raw glass and the transmission of glassmaking recipes and knowledge. This article extends that focus by examining the subsequent transformation of raw glass into finished objects, using enamelling as a central case study. We argue that enamelling was a distinct, skill-intensive practice requiring specialised knowledge separate from that of glass production. Combining historical source analysis with experimental reconstructions, the study investigates how fire management critically influenced enamel quality. By applying a range of firing techniques to reconstructed seventeenth- and eighteenth-century enamels, we demonstrate that variability in heat application significantly affected the final outcome. Our experiments suggest that historical enamellers developed a deep, practice-based understanding of several key factors: (i) controlling heat for optimal adhesion and colour development; (ii) manipulating flame intensity and furnace atmosphere to enhance bonding; and (iii) employing layering techniques to improve durability. These findings invite a rethinking of fire not merely as a tool, but as an active and variable ingredient in the enamelling process.